The invention relates to a bone screw. In particular, the invention relates to a bone screw that can be used as a fusion screw. This screw promotes fusion in the surrounding bone.
A bone screw of this kind is known from US 2004/0015172 A1. This bone screw has a tubular thread section with a bone thread and with a plurality of recesses in its wall. A head and a tip can be connected to the tubular thread section. In use, the tubular portion can be filled with bone material or other growth-promoting material and then the tip and/or the head are connected to the tubular portion. First, a core hole is prepared, then the screw is inserted into the core hole and screwed into the bone. After a certain period, fusion between the screw and the bone takes place. The screw can act as a traction element to connect shattered or split off parts of bones together by means of the screw. To avoid the preparation of a core hole, the tip can be self-cutting.
Similar bone screws are known for example from US 2004/0122431 and US 2004/0147929 A1.
Further, so-called injection screws, for example such as described in WO 01/26568 A1 are known, which are used to inject bone cement or other liquid or pasty material into the bone. This kind of screw has a relatively thin cannula extending within a bone screw. The cannula is not suitable for being filled with bone chips or bone graft.